Consider I want to build package against specific module stream, I'd like to
be able to specify this by mock's option.
Well, you have:
## This will only work with DNF and when repo is configured with modules=1 for repo in dnf.conf.
## This is executed just before 'chroot_setup_cmd'.
# config_opts['module_enable'] = ['list', 'of', 'modules']
# config_opts['module_install'] = ['module1/profile', 'module2/profile']
I do not think this need special command line. Especially when we have `--config-opts=KEY=VALUE`.